This invention relates, in general, to heat exchangers and methods of constructing heat exchangers; and, in particular, this invention is useful in the field of non-contact heat recovery steam generators.
Heat recovery steam generators are non-contact type heat exchangers which include fluid carrying tubes disposed in a hot gas path. One example of such a device is shown in U.S. Pat. No. 4,262,705 to Skinner et al. assigned to the assignee of the present invention. Such an arrangement is sometimes referred to as a tube and plate construction because the fluid carrying tubes are supported by a plate having tube carrying holes formed through the plate. Heat recovery steam generators are useful in combined cycle power plants such as that shown in U.S. Pat. No. 4,316,435 to Nagamatsu et al. also assigned to the present assignee. In the Nagamatsu et al. patent a "U" tube construction is shown which comprises inlet and outlet pipes each connected to its respective complement pipe by a single "U" shaped return bend. There is another type of tube arrangement which utilizes serpentine tubes, as hereinafter described which include a number of straight pipes interconnected in series flow by a plurality of return bends. A serpentine arrangement of tubes utilized in combination with a tube support plate requires that the return bends be welded to the straight pipes after the straight pipes have been inserted through the tube plate holes. This results in less than desirable weld fabrication and test conditions while increasing the fabrication costs.